The Natural Nuclear Reactor of Gabon Africa

and how it may have

Initiated its Sustained Reaction

By Rex A. Crouch

Copyrighted © by Rex A. Crouch, 2008

The Natural Nuclear Reactor of Gabon Africa and how it may have Initiated its Sustained Reaction

By Rex A. Crouch

Abstract

This paper examines natural nuclear reactions by looking at the natural nuclear reactor in Gabon, Africa, and

speculates on what may have caused the reaction to initiate.

The natural nuclear reactor is addressed in detail deriving information from multiple sources to establish how the

reactor functioned and sustained operations, and create a foundation to support my concept of how the reactor

initiated the fusion process. Through the paper the following is addressed:

How 16 reactor zones worked for more than 150 million years on a 30 minutes on, and 2 hours and 30

minutes off cooling cycle while using the ground waters to moderate the reactions and how the reactor

ultimately shut down operations 1.8 billion years ago

Speculation on how the reaction initiated relying on maps of tectonic plates through geologic time and

overlaying known recoverable uranium deposits on geologic maps to understand where the uranium was.

The paper concludes that nuclear energy is safe, and that radioactive waste is a natural occurring event and can be

contained by geology, and speculates that the radiation may have been beneficial to the development of mammals.

The Discovery of the Natural Nuclear

Reactor.

France is a country that embraces nuclear power

providing more than 75% of its electricity needs

by operating 59 nuclear power plants. Given

this, France conducts exploratory mining, and

uranium mining in many places around the world

[8].

The country of France was mining in Gabon

Africa for uranium when they discovered that

something was incorrect in the ratio of elements.

In nature there are several types of uranium but

there are two predominate isotopes. These

uranium isotopes are U235 and U238

and as they

are radioactive elements they are subject to

decay. This decay however occurs at different

rates because the uranium is of different isotopes

but they still maintain the same ratios wherein

U238 comprises about 99.3% of all uranium in an

ore deposit and U235 constitutes the other .7% in

any given ore deposit. As these ratios were not

found in the ore recovered from Gabon in was

ultimately found that the U235 species had

already been depleted [18].

Scientists from around the world argued against

this concept, and insisted that the uranium had

been displaced but that nature could not have

depleted the U235, as too many intricacies were

involved in conducting a nuclear reaction. It was

demonstrated that the level of U235 found in

Gabon could only be found after depletion in a

nuclear reactor and there was no proof offered to

support the displaced U235 concept. With no

other plausible explanation, the topic of how a

natural reaction occurred was pursued [18].

The Operation of the Nuclear Reactor

Operating a conventional nuclear reactor is

difficult as it requires a specific cooling rate, and

the fuel must be introduced at a specific speed to

ensure there is neither an explosion, nor a

burnout. How nature depleted the uranium

became the topic of discussion.

We can se in the basic profile depiction of the

Gabon area, from the U.S. Department of

Energy, that the uranium ore deposits are located

in a sandstone bed. This sandstone was

inundated with water which served to cool the

reaction, facilitating a 150,000 year long nuclear

reaction, finally ended 1.8 billion years ago.

U.S. Department of Energy (image 1), [18], [19].

As mentioned earlier, U235 typically consist of

about 0.7% of the uranium content. These two

species have different half-lives, thus decaying at

slightly different rates. Calculating the half-lives

of U235 and U238

back 1.8 BYA, there would

have been three percent more U235 than present,

and that may have been enough to facilitate a

natural reaction. This will be a topic of

discussion further-on.

The more in-depth look at the reaction site as

addressed by the research paper „Record of

Cycling Operation of the Natural Nuclear

Reactor in the Oklo Area in Gabon‟ details the

actions of the reactor site [2] and [18].

During the course of the research it was found

that 16 separate reactor zones operated in the

Oklo area of Gabon. The remaining amounts of

U235 as well as the amounts of Pu239

resultant

from fission present in the system indicated that

no less than five tons of U235 was consumed

releasing about 15 GW of nuclear energy per

year. The plutonium‟s half-life, the half-life of

Pu239 is 24,000 years. Given this half-life, an

estimate for an effective fission chain could have

lasted for about 150,000 years in Gabon. Over

the course of 150,000 years the reactor produced

an average of 100 kW which is equivalent to the

power produced by a nuclear research reactor

[2], [18], and [20].

There were several theories for the cooling

mechanism that allowed for the self regulation.

One possibility presented was the burning of

neutron absorbing isotopes, however, proof for

the water cooling theory was found in anomalous

xenon of alumophosphates which identified a

specific cycling process with a time scale. As

the reactor temperature increased the “unbound”

water was vaporized. At this point the neutron

thermalization would reduce and the reaction

would shut down. As the waters cooled, and

condensate reducing the temperature of the

reactor, the reaction would reignite [2] and [13].

This was strongly emphasized to me in an email

correspondence with the Yucca Mountain

Research Team. They also stressed that the

Pu239 produced did not move more than 10 feet

away from where it was created. That this

system was not only self-regulating but also self-

contained. This ensured the environment was

not inundated with radioactive material which

was of special interest to the Yucca Mountain

research team [21].

Understanding the cyclic process was the next

step in understanding the reactor. It was found

that Tellurium was the most retentive fissionable

product in the reactor zones. The measured

amounts of fission Te isotopes were exact

matches for the theoretical amounts.

Subsequently, all of the tellurium -active

precursors were also retained in the reactor

material. This led the researchers to assume that

I129 had also been retained in the reactor

material. Because these materials were retentive

they migrated within the system from the

uranium oxide to the alumophosphate. After

migrating to the alumophosphate they could

decay to a xenon. A key to understanding the

cyclic process was in determining that the

alumophosphate was only retained when the

reactor cools between its “operational pulses”.

The researchers ultimately found that “high

concentration of short-lived intermediate fission

products in alumophosphate without significant

quantities of uranium implies that it precipitated

during the operation of the Oklo reactor.” The

researchers conducted hydrothermal experiments

to demonstrate that alumophosphates grow fast

at temperatures of Cto300270 , a rather low

temperature. After a fission product is captured

by one of these fast growing alumophosphates it

remains in place decaying to Zeon. The Zeon

can be released if the temperature rises above the

blocking temperature of the alumophosphate

however the temperatures never got this high

during operating pulses of the reactor. In

accounting for all of the isotopes and their

evolutionary stages, the I129was not matching

the proportions of any of the other elements.

The researchers ultimately made an assumption

that 37% of the I129 had been lost by the

alumophosphate since the reactor shut down.

The I129 has a half-life of

61016X years and is

chemically active forming water soluble

compounds so it was possible that it was leaked

into the aqueous environment. The researcher

pursued this line of reasoning and found that

there was compelling evidence that the I129 did

leak into the aqueous environment. The ratios of

the radioactive elements in an unbounded water

environment suggest that the reactor functioned

in pulses of 30 minutes: converting the water to

steam, removing the sustained cooling agent

which made the reactor subcritical and the

reactor cooled for 2 hours 30 minutes while the

water returned to the reaction zone [2].

The Development of Recoverable Uranium

As the source of the Gabon Reactor is a

“recoverable source”, meaning it can be mined to

recover the mineral, I will look specifically at

recoverable uranium.

While uranium is found worldwide, recoverable

uranium occurs in sandstone formations. The

uranium developed in the sandstone – the Earth‟s

mantel has an abundance of uranium as well as

other elements. These elements reached the

surface of the Earth through volcanism. The

uranium was then leached from the volcanic

rocks oxidizing the oceans. Sandstone

formations serving as aquifers collected, and

consolidated the uranium as the uranium was

precipitated in the sandstone [3] and [12] .

Sedimentary rocks did not begin to fully form on

the Earth until 2.5 BYA (during the Proterozoic)

[4]. For this reason it is not reasonable to

believe that the recoverable uranium was

emplaced prior to this date.

To back track and see where the recoverable

uranium formed and when, we need to look at

the present. The majority of the world

recoverable uranium is located in the following

location in the given percentages where

percentage of less than 5% are not mentioned

and the percentage of Antarctica is high however

not fully known as mining is prohibited there [1],

[15].

Tons U Percentage of

World

Australia 1,143,000 24%

Antarctica ! ! %

Kazakhstan 816,000 17%

Canada 444,000 9%

USA 342,000 7%

South Africa 341,000 7%

Namibia 282,000 6%

Brazil 279,000 6%

Percentages of recoverable uranium, Table 1, [14].

With the amounts of recoverable uranium known

today, I superimposed the known locations on

geologic maps.

Looking at the Devonian period we see that the

necessary landmasses were present to collect the

above percentages of uranium with the location

indicated by an orange overlay:

Evolution of the Earth Text, Image 2, [5].

By the time of the Permian, all of the land that

currently has recoverable uranium was fully

exposed as depicted in the below Permian map,

and once again the recoverable uranium locations

are indicated by the orange overlay:

Evolution of the Earth Text Image 3, [5].

The Gabon Reactor Zone is annotated in the

above map by the red dot. The reactor began

operations about 1.8 BYA [6].

This demonstrates that high amounts of uranium

were available throughout the world and it is

known that the ratios have been consistent

worldwide yet the reaction took place in one

place only. This establishes the foundation for a

question.

Speculating on why the uranium deposit

began a nuclear reaction.

There are numerous documents explaining the

geology of the Gabon site, the physics of the

reaction, how the reaction was sustained, and

why it finally quit after 150,000 years of activity,

and even documentation how the environment

contained the radiation.

The uranium was probably in place for about 500

millions of years based on when sandstone was

first available to allow the deposition of uranium

to occur. Since all of the components were there,

why didn‟t the reaction happen sooner? If all of

the uranium ratios between U235 and U238

are

constant today then they must have been

constant, and emplaced at about the same time in

the past; the decay rates would be about the same

thus leading us to believe that the uranium

contents worldwide would have 3% more U235

than present. If the whole world had 3% more

U235 why did the reaction take place in one only

location containing only 6% of the recoverable

uranium as opposed to some place else such as

Australia with 24% of the recoverable uranium?

Why did the reaction occur at all? [14], [15].

First look at what causes a nuclear reaction to

help answer this question. The three main

components that produce a nuclear reaction are

[16]:

1. Refined fuel or density of fuel

2. Heat

3. A long confinement period

We will ensure that all of the components are

available as we address these questions.

In attempting to answer these questions I have

poised, it is also helpful to look at the conditions

when the reaction occurred. At this time when

the site initiated a nuclear reaction it was 1.8

BYA, the world was in the Proterozoic. The

conditions were:

Presented below as Image 4, the portion

of South America and portion of Africa

had developed together during the

Archean and began rifting for the first

time during the Proterozoic. This rifting

action happened again during the

Mesozoic but without the same effects

[7].

Encyclopedia Britannica, Image 4

World water levels were low in the pre-

Sloss sequences [4].

A spreading center developed separating

the Archean masses and the later

Proterozoic masses as depicted by the

circle I provided in the center left portion

of Image 4 above.

It is my opinion that the reaction initiated for the

following reasons:

A continental rift occurred spreading the

two continents apart very near the Gabon

reaction site. At the point of the rift the

Earth‟s crust thinner. At this spreading

center, the sandstone aquifer in the area

was probably drier than normal as the

world water levels were in a low pre-

Sloss sequence state. These

combinations possibly lead to higher

temperatures in the area of reaction.

There was a vertical induced force caused

by the rifting, a downward force caused

by gravity, and these were combined with

the horizontal force induced by the

Poisson effect caused by the two

aforementioned forces at the uranium

site. The Poisson effect was more

profound in the sandstone with a Poisson

ratio of 0.3 wherein the uranium deposits

were far more rigid with a Poisson ratio

of 0.23. These amounts are respectably

comparable to polystyrene foam and

steel. As the sandstone could flex to

compensate for the forces being applied,

a significantly higher pressure was being

applied to the more rigid uranium

deposits [9], [11], [17], and [19].

Heat and pressure may alter the ratio of

carbon isotopes [10]. It would stand to

reason that similar ratio changes could

occur in all native elements. This

condition of added heat, and pressure

may have contributed to an even higher

ratio change in uranium isotopes causing

a higher than normal U235 percentage as

well as extreme pressure, and

temperatures.

Reviewing this sequence – These above reasons

for the reaction meet the three previously

mentioned requirements for a nuclear reaction. I

believe that the U235ratio changed through heat

and pressure resultant of the continental rifting;

the rifting created enough pressure to initiate a

reaction, the rifting allowed ocean waters

necessary to cool, and sustain the reaction to

enter between the continents and subsequently

reach the Gabon site to sustain the reaction for

150,000 years until dispersion between the

U235isotopes were so great that the reaction

could no longer sustain itself.

Summary

Earth deposited the uranium, refined the ratio to

create a natural nuclear reaction, and provided

heat, and pressures to initiate the reaction as well

as a cooling sequence. As this reactor was

operating when Stromatolites were creating our

atmosphere, and used the aquifer coolers in the

same lands that eventually served as the

evolutionary nursery for many reptiles,

mammals, and even humans there is no reason to

suspect that this uncontained reactor had a

derogatory effect on nature. Nuclear reactions

are a natural event, and the geology of our planet

does contain the event and the heavy metals that

result from the reaction – our planet possibly

even benefits from such events.

Works Cited Bibliography.

[1] Antarctica Official Web Page

http://www.vb-tech.co.za/Antartica/

This is an official web site for Antarctica providing scientific data and research as well as

listing treaty information.

[2] A.P. Meshik, C.M. Hohenber, and O.V. Pravdivtseva. “Record of Cycling Operation

of the Natural Nuclear Reactor in the Oklo/Okelobondo Area in Gabon”. American

Physical Society Volume 93, Number 18. 29 October 2004.

This was a study of the Gabon area using laser extraction techniques and ion-counting

mass spectrometry to provide accurate record of cycling.

[3] Carlston College, Uranium Deposits on Navajo Nation

http://serc.carleton.edu/research_education/nativelands/navajo/uraniumdeposits.html

This is a discussion of the uranium mining impacts and how recoverable uranium is

formed in sandstone.

[4] D. R. Prothero and R. H. Dott. Evolution of the Earth, 6th

Edition. 2004

This is the text book used for MTU Geology 3320, Earth History, instructed my Dr. J.R.

Wood. 2006

[5] D. R. Prothero and R. H. Dott. “Image 2” and “Image 3” Evolution of the Earth, 6th

Edition. 2004

These images were derived from the Evolution of the Earth text book. The author

superimposed the known recoverable uranium deposits on these to images.

[6] D. F. Hollenbach and J. M. Herndon. Deep-Earth Reactor: Nuclear Fission, Helium,

and the Geomagnetic Field. National Academy of Sciences 23 July 2001. Authored for

U.S. Government under contract No. DE-AC05-00OR22725.

This is an in-depth study of deep-earth reactors and utilizes the Gabon reactor for near

surface examples.

[7] Encyclopedia Britannica, Proterozoic Map. “Image 4”.

http://www.britannica.com/eb/art-1708

[8] Information for Nuclear Energy Information Center, Aug 2006.

http://www.uic.com.au/nip28.htm

This is a paper produced by the Australian Nuclear Energy Information Center on

France‟s nuclear energy program and uranium mining and consumption.

[9]Poisson ratio of sandstone, University of California, Davis California Geology

Department, 2006.

http://www.geology.ucdavis.edu/~gel101/gel101_hw13.pdf#search='sandstone%20poiss

on%20ratio'

This is a geology department document that states the Poisson ratio of sandstone.

[10] G. Faure, Principles of Isotope Geology, (John Wiley & Sons), 2nd

Edition, 1986.

This is a text book on Isotope Geology which focuses on radiometric age dating.

[11] G.H. Geiskic, Poisson ratio of uranium, Department of Energy, Energy Citations

Database. 1980

http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=5028050

This is a reference paper stating the Poisson ratio of uranium.

[12] R. Gehriger. Smart Uranium. “The inglorious legacy of COGEMA in Gabon -

Decommissioning of the Mounana uranium mine and mill site.” September 2004

http://www.wise-uranium.org/udmoun.html

This is a German environmental perspective on the impact of uranium mining in Gabon

[13] R. C. Ewing, Corrosion of Spent Nuclear Fuel: The Long-Term Assessment,

University of Michigan Environmental Management Science Program, Project ID

Number: 73752 June 2003

This is a microscopic look at how radiation was contained at the Gabon, Africa site.

[14] Table of Recoverable Uranium Percentages, Table 1, 2006.

This is a table I developed combining information from the Antarctic site and from the

World Nuclear Association to depict large scale (equal to or greater than 5% of

recoverable uranium on Earth)

[15] The World Nuclear Association, Recoverable Uranium. June 2006

http://www.world-nuclear.org/info/inf75.htm

This is an information paper on the availability and recoverability of uranium in the

world providing percentages of recoverable uranium worldwide.

[16] Think Quest, “Nuclear Fusion”.

http://library.thinkquest.org/3471/fusion.html

[17] University of Wisconsin Madison, Poisson Effect.

http://silver.neep.wisc.edu/~lakes/PoissonIntro.html

This is a UWM document describing the Poisson Effect and making comparison of ratios.

[18] U.S. Department of Energy, Fact Sheet

http://www.ocrwm.doe.gov/factsheets/doeymp0010.shtml

This is the Department of Energy non-technical fact sheet on the Gabon reactor and how

it safely contains nuclear waste while relating the site to the Yucca Mountain nuclear

waste site project.

[19] U.S Department of Energy image of profile view of uranium ore body in western

Africa image 1

http://www.ocrwm.doe.gov/factsheets/images/0010_gabongeology.gif

This is the non-technical illustration of the reactors being contained inside the

sedimentary layers of sandstone.

[20] U.S. Nuclear Regulatory Commission. October 2003, revised December 2004.

http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/plutonium.html

This is a governmental fact sheet on plutonium providing all relevant data.

[21] Yucca Mountain Research Team, email message to author. 9 November 2006.

This is an email response to mailed written questions I had regarding the cooling

mechanism of the nuclear reactor.